Is there any disadvantage of the maximum number of fitness function call as a stop criterion?
I imagine that using the MaxNFFC as a stop criterion only happens in very particular implementations. And this is its main disadvantage.
Normally, you'd evaluate each individual, each generation. So, NFFC will always be the same as the size of the population times the number of epochs (+1 to consider the initial population).
$$N*(E+1)$$
As the population size is generally constant, MaxNFFC looks a lot like an MaxEpoch stop.
$$ \frac{\text{NFFC}}{N} = E + 1 $$
So, it seems that it might be used in scenarios where:

the population size is not constant (in this case you want to make sure that at least K individuals have been evaluated before stopping).
not all individuals are evaluated each epoch. There might be a high abortive rate (individuals with invalid genomes that are kept in the population but not considered). In this case, as above, you want to perform a minimum amount of evaluations.

I wouldn't see the usage of MaxNFFC in other cases.